This invention relates to ink reservoirs for thermal ink jet ("TIJ") print cartridges.
TIJ technology is widely used in computer printers. Very generally, a TIJ includes a print head typically comprises several tiny controllable ink jets, which are selectively activated to release a jet or spray of ink from an ink reservoir onto the print media (such as paper) in order to create an image or portion of an image. TIJ printers are described, for example, in the Hewlett-Packard Journal, Volume 36, Number 5, May, 1985, and Volume 39, Number 4, August, 1988.
In TIJ pens it is necessary to connect the ink reservoir to the print head. The size of this connection affects the design of the printer that the pens are used in. An ideal reservoir-to-print-head coupler, from a printer design point of view, would be no longer than the TIJ head is long, and would be high or tall enough to allow the drive and pinch wheels to get as close to the print head as possible. Any increase in the size of this coupler will compromise the paper handling ability, which may affect the print quality, and increase the size of the printer. Smaller printers are desirable as they conserve desk space and the materials from which the printer is fabricated.
An intended application for this invention is for a spring bag TIJ pen, although it is not limited to the spring bag pen. In one exemplary spring bag pen design, the pen frame made of a first molded material is lined with a second molded material, such as polyethylene, on the inside to produce a surface suitable for staking the films of the spring bag. The first molded material from which the frame is made could be, for example, an engineering plastic, and provides the necessary structure for the pen which could not be accomplished with the second molded material. This invention relates to the fluid connection of the first and second molded materials in such a way as to provide a space-efficient, leak-resistant connection.
Conventional methods of connecting materials include the use of glue, seals, such as gaskets or O-rings, or mechanical press fits. In these cases two or more separate parts are fabricated and assembled together to form a single unit. Each part must be designed and sized with respect to its needs in manufacturing, structural integrity, and with the tolerance of the mating part in mind. Such joints as these take up much more space than joints fabricated in accordance with this invention. In addition to taking up much space, the traditional methods produce a joint whose reliability can be affected by the part tolerances, surface finishes, and the assembly operation. The method of this invention provides a joint which is less susceptible to surface finish defects than joints obtained by such traditional methods.